1. Field of the Invention
This invention relates generally to an image forming system and, in particular, to a system and method of automatically testing degradation of stepper motors in an imaging apparatus.
2. Description of Related Art
Electrophotographic printing systems, such as digital copiers, are widely used in industry. In a digital imaging machine, an image of a document is captured by an input scanning facility, and converted into selected digital image data. A control unit then typically compresses this image data, then either forwards it to a suitable printing module or stores it in system memory.
A production printing system contains an inherently high premium for reliability and uptime since downtime represents a potential loss in profits to a business. The printing system may have as many as 30 stepper motors. The stepper motors are located throughout the machines and are used to enable any number of machine functions. Many stepper motors are used in the paper path. Paper jams, a major source of customer inconvenience, are often caused by a small disturbance in machine timing, such as that which might occur in the case of a stepper motor missing a step or hesitating. These problems, being intermittent are very difficult to diagnose. While stepper motors are generally considered reliable, there are always exceptions, and the mechanical assemblies that they drive could potentially have significant failure rates.
A method and apparatus for diagnosing whether a solenoid in an imaging forming system is functioning properly is disclosed in U.S. Pat. No. 6,326,898 B1 and includes sending an actuating current to a particular solenoid while a current waveform and elapsed time such as pull-in time value are noted for instances when the solenoid is in a first position and a second position. The first position can be one in which a solenoid plunger is extended and the second position can be one in which the solenoid plunger is retracted, or vice versa. Based at least partially on the measured actuating current values prior to the beginning and after the ending of solenoid movement, and measured time values, a determination can be made as to whether the solenoid is functioning properly by comparing these values to predetermined values for a properly functioning solenoid.
Hence, there is still a need to predict when a stepper motor needs to be replaced before failure occurs.
Accordingly, pursuant to the features of the present invention, a printing apparatus is disclosed that includes a stepper motor automated self-test routine that gives an approximation of the state of degradation of the stepper motor and/or its driven load. The test includes artificially increasing the starting frequency and/or reducing the operating current by a known and controllable amount to a stepper motor and tracking the level at which the motor is just able to start operating. By examining the magnitude and/or change in these levels, the remaining life and reliability of the motor can be predicted. This information can then be conveyed to a service technician either locally or remotely to initiate a repair/replace action, thereby reducing unscheduled maintenance.
Alternatively, the self-test routine could be used in conjunction with existing paper path sensors to detect the occurrence of a successful start and determine the start time for a stepper motor. The start times are stored for trend analysis.
These and other features and advantages of the invention are described in or apparent from the following detailed description of the exemplary embodiments.